Various types of electronic apparatuses such as smart phones, smart watches, and smart glasses have been recently developed. Moreover, due to the emergence of the Internet of Things (IoT), home appliances, wearable devices, etc. include a variety of input devices such as key buttons, touch screens, and touch pads. However, as electronic apparatuses decrease in size, limitations on space where input devices can be arranged increase. In addition, there is the demand for types of inputs that are capable of easily interacting with electronic apparatuses without requiring a user's attention.
Thus, sound inputs, gesture inputs, and the like may be used in addition to existing keyboard inputs, touch inputs, etc. However, since the sound inputs are vulnerable to ambient noise and may be heard by other people, the sound inputs may be illegally used. Other electronic apparatuses may react to the sound inputs instead of an electronic apparatus that a user may intend to manipulate.
Since the gesture inputs may be easily viewed by other people, the gesture inputs may be illegally used. Also, expensive sensors are required to detect the gesture inputs.
For user authentication, various types of inputs such as password inputs, gesture inputs, and biometric signals are used on electronic apparatuses. However, the password inputs and the gesture inputs may be easily used by other people. The biometric signals are inputs using biometric signals extracted from, for example, DNA, ear structures, irises, retinas, face recognition, fingerprints, finger structures, hand structures, a gait, odors, veins, voice, and the like. Such biometric signals are less likely to be used by other people, and even if they are stolen, it is impossible to change them.